Waterflow
The Kawai Nui Flood Control Project closed the water flow connecton between Kawai Nui Marsh and Kawai Nui Stream and rerouted the water to flow out through Oneawa Canal. Today there is no connection between the Hamakua Canal Extension and Kawai Nui Marsh.

Surface runoff and storm drains from surrounding residential areas of Coconut Grove and the commercially zoned area of Kailua Town drain into the Hamakua Canal Extension. The extension connects to the lowland Kae'elepulu Stream which periodically empties into Kailua Bay.